1. Field of the Invention
The present invention relates to a fuel cell which has a cylindrical shape in which a plurality of cells are formed on a substrate tube, a method for manufacturing the same, and an application apparatus used for manufacturing the same.
2. Description of Related Art
A solid oxide fuel cell (hereinafter, referred to as “SOFC”) is a fuel cell in which ceramics such as zirconia ceramics are used as an electrolyte, and city gas, natural gas, petroleum, methanol, coal gasified gas and the like are used as a fuel in order to operate the fuel cell. As one of SOFCs, a cylindrical fuel cell is known. A cylindrical fuel cell contains a plurality of cell stacks inside a power generating chamber. In a cell stack, a plurality of cells including an anode (a fuel electrode), a solid electrolyte film and a cathode (an air electrode) stacked in a circumferential direction of a substrate tube are formed. The plurality of cells are arranged in an axial direction of the substrate tube, and the adjacent cells are electrically connected in series via an interconnector.
On manufacturing the aforementioned cylindrical fuel cell, the anode, the solid electrolyte film and the interconnector are first formed on the substrate tube. Thereafter, the anode, the solid electrolyte film and the interconnector as well as the substrate tube are co-sintered. The cathode is formed on the solid electrolyte film after it has been co-sintered.
The surface of the co-sintered substrate tube is uneven since the anode and the like are formed thereon. Further, the substrate tube may be warped in a longitudinal direction. Therefore, in Japanese Unexamined Patent Application, Publication No. 2013-175305, instead of screen printing, a dispenser is used to form a cathode so that the cathode having a uniform film thickness is formed on the uneven substrate tube. Further, the fine adjustment of a discharge position of the dispenser is possible, and thus, the accuracy of forming the film can be improved.
As a conventional method for applying an application material, methods disclosed by Japanese Unexamined Patent Application, Publication No. Hei 3-91998 and Japanese Unexamined Patent Application, Publication No. 2010-167322, for example, are known. Japanese Unexamined Patent Application, Publication No. Hei 3-91998 discloses a technique in which, when chip-shaped electronic components such as a resistor, a capacitor and a transistor, are temporarily fixed at respective predetermined positions on a printed board, an adhesive is applied on the board by taking a warp, a curve, a level difference and the like of the board into consideration. More specifically, Japanese Unexamined Patent Application, Publication No. Hei 3-91998 discloses that a noncontact distance sensor such as a laser displacement sensor is attached to an applying head part discharging an adhesive, distance measured by the distance sensor is fed back as an elevating/lowering amount of the applying head, whereby stable attachment operation such as application of the adhesive to the printed board are performed.
Japanese Unexamined Patent Application, Publication No. 2010-167322 discloses that by using not a noncontact distance sensor such as a laser displacement sensor but a contact distance sensor which is cheaper, application of an adhesive is performed.
As illustrated in FIG. 6 of Japanese Unexamined Patent Application, Publication No. 2013-175305, in the cathode formed by the method disclosed by Japanese Unexamined Patent Application, Publication No. 2013-175305, both end portions in the longitudinal direction of the substrate tube have gentle slopes. At the ends of the cathode, the film thickness of the cathode decreases toward a portion connected with the interconnector. The portion having a thinner film of the cathode has low electrical conductivity, and therefore, a conductive path becomes thin and connection resistance with the interconnector becomes large, as a result. The shape of the cathode described above causes decrease in power generating performance.
In order to obtain a sufficient conductive path with an interconnector with a cathode having the shape disclosed by Japanese Unexamined Patent Application, Publication No. 2013-175305, a size of each cell is required to be large, whereby resulting in decrease in effective power generation area capable of contributing to power generation. Therefore, there is a limit to increase in power generation amount with one cell stack.
In the processing for forming the cathode described above, on an outer surface of the cylindrical cell stack, slurry for cathodes is applied so as to have a stripe pattern with intervals. Here, since the cell stack has a long body, for example, with a length of one meter or more, the center part of the cell stack is warped by the gravity. Moreover, since application of the slurry for cathodes is performed with the cell stack rotated around an axis, the rotation causes even displacement of the axis.
In order to cope with such displacement of the axis, slurry for cathodes is, conventionally, sprayed on an outer peripheral surface from a slightly distant place. In application of slurry for cathodes by spraying, however, it requires a long time for the slurry for cathodes to have a desired film thickness. Also, since spraying makes a machine worn out, the exchange frequency of components of the machine increases, resulting in a problem that the cost is increased.
Such problem is not specific to a SOFC, and the problem often occurs in a case where an application material is applied on an outer peripheral surface of a rotating cylindrical member.
The present invention has been made in view of the aforementioned problem, and the object thereof is to provide a fuel cell which has high power generation performance, a method for manufacturing the same, and an application apparatus used for manufacturing the same.
Another object of the present invention is to provide an application apparatus capable of applying an application material to a cylindrical member rotating around an axis (e.g., a substrate tube), with low cost, efficiently, and with a stable quality.